In passenger cars with high-performance internal combustion engines, which are preferably designed as V-engines, the exhaust gases are frequently sent from the two cylinder banks via two manifolds in two exhaust gas lines to a common end muffler or to two separate end mufflers. The two exhaust gas lines extend here in the vehicle on the underbody in a tunnel, which has heat protective shields at regularly spaced locations upwardly and to the side. The ground clearance represents an imaginary limit of the tunnel in the downward direction. Furthermore, a middle muffler, which must be arranged in the middle area of the system, can frequently be found for acoustic reasons. A separate middle muffler can be assigned here to each exhaust gas line. A common middle muffler can likewise be assigned to both exhaust gas lines. At any rate, the particular middle muffler must likewise be accommodated in the tunnel, which regularly leads to problems in terms of the space available for installation, because the particular middle muffler must have a certain minimum volume in order to be able to assume its acoustic function.
An exhaust system, which has two separate exhaust gas lines for removing exhaust gases of an internal combustion engine, is known from EP 1 400 666 A1. The prior-art exhaust system comprises, furthermore, a switchable sound transmission means, which couples the two exhaust gas lines with one another for transmitting airborne sound. The sound transmission means can be activated and deactivated by means of a control means, and this takes place as a function of at least one operating parameter of the internal combustion engine. For example, the rpm (revolutions per minute) and/or the load of the internal combustion engine are suitable operating parameters here.
The prior-art exhaust system is advantageously operated such that the sound transmission means is active at low rpms. Mufflers that are assigned to the exhaust gas lines are designed acoustically for interfering frequencies, which appear at low rpms. The sound transmission means is deactivated at higher rpms, as a result of which the effective interfering frequencies are reduced by half based on the specific assignment of the separate exhaust gas lines to individual cylinders of the internal combustion engine. Effective muffling can thus be achieved for two rpm ranges, which are related to one another via the interfering frequencies. The drawback is the limitation of the muffling action to only two rpm ranges. Furthermore, the activation of the sound transmission means at low rpms may lead to a reduction of the available engine torque because of disadvantageous effects on the charge cycle operation in the cylinders of the internal combustion engine.